The present invention relates to the field of nuclear reactors, and in-core instruments used to measure physical characteristics inside the nuclear reactors.
In-core instruments (ICIs) are used to measure the power level and temperature of a nuclear reactor while it is in operation. In some reactors, the insertion of the ICIs into the reactor requires the ICIs to be traversed through complicated, winding guide paths to reach their final location.
The current technology uses a strip wound metal hose (SWMH) to contain the individual detectors included in an ICI assembly. The SWMH material is flexible and allows the ICI to negotiate the turns in a guide path as it is inserted into the reactor. However, the SWMH is not watertight and thus allows the reactor coolant water to be in direct contact with the detectors. Experience has shown that under certain circumstances the water can cause pitting and cracking in the wall of the detector. If water penetrates the detector wall, the detector will fail.
It is required that a minimum number of these detectors always function. If the minimum number of detectors is not functioning, the reactor can not operate at full power.
It is therefore an object of the present invention to provide a flexible housing for detectors that are part of an ICI. It is a further object of the invention to provide a housing that will prevent the detectors and other ICI assembly applications from becoming exposed to reactor coolant and the high-pressure conditions within the nuclear reactor.
It is an object of the present invention to meet the above-described needs and others. Specifically, it is an object of the present invention to provide a protective hose for an in-core instrument assembly used in a nuclear reactor. The hose includes a first end that is hermetically sealed to a first member of in-core instrument assembly such as a bullet nose, a second end that is hermetically sealed to a second member of said in-core instrument assembly such as a seal plug, and a body portion that surrounds at least one detector in the in-core instrument assembly, and has flexible, corrugated outer and inner surfaces. The body portion includes a series of ribs having peaks. The hose is compacted in length to a degree that the peaks of the ribs are substantially adjacent to one another. The ribs also have side surfaces that decline from the peaks to valley portions that are disposed between the side surfaces. The hose is compacted in length to a degree that the side surfaces are completely in physical contact with one another.
Because the ends of said hose are hermetically sealed to the in-core instrument assembly., the hose provides an airtight and watertight enclosure for the detector(s). The hose is made of a non-corrosive metal, such as stainless steel, to ensure that the enclosure retains its watertight and airtight features despite the harsh conditions inside a nuclear reactor.
It is a further object of the invention to provide a method for manufacturing an in-core instrument assembly, that includes the steps of providing a central tensile member, providing at least one detector in the vicinity of the central tensile member, providing a flexible hose having ribs that define corrugated inner and outer surfaces, surrounding the central tensile member and detector(s) with the hose, and hermetically sealing the ends of the hose to the in-core instrument assembly so that the detector(s) are enclosed in an airtight and watertight space.
The flexible hose is collapsed to reduce its length prior to the step of surrounding said central tensile member and said at least one detector with said hose. The ribs of the hose have peaks so that the hose, when collapsed, is compacted in length to a degree that the peaks are substantially adjacent to one another. Furthermore, the ribs have side surfaces that decline from the peaks to valley portions that are disposed between the side surfaces. When collapsed, the hose is compacted in length to a degree that the side surfaces are completely in physical contact with one another.
It is yet a further object of the invention to provide a method of manufacturing a flexible hose for an in-core instrument, which includes the steps of providing a flexible hose made of a non-corrosive material, having ribs that define a corrugated outer and inner surfaces, and subjecting the hose to a collapsing process, so that the hose is compacted in length. The ribs have peaks that define an outermost diameter of the hose, and side surfaces that decline from the peaks to valley portions that are disposed between the side surfaces. The portions of the inner surface of the hose that define the valley portions also define an innermost diameter of the hose. The hose has peaks and side surfaces that decline from the peaks to valley portions that are disposed between the side surfaces. When collapsed, the hose is compacted in length to a degree that the side surfaces are completely in physical contact with one another.
The collapsing process can be a hydro-collapse process, and includes the steps of fitting a rod inside of the hose, along the hose""s length, and providing hydro-pressure to the hose. The method can also include the step of heat treating the hose prior to subjecting the hose to a collapsing process. The method can further include the step of sealing one end of the hose to a first member of the in-core instrument, and sealing the other end of the hose to a second member of the in-core instrument.
Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims.
To achieve these stated and other objects, the present invention may be embodied and described as